One process for the preparation of TEM-lamellae is described in the patent application DE 10 2009 008 166 A1, the content of which is incorporated herein by reference in its entirety. According to this application, a protective strip is generated on the substrate surface, and then the substrate material to both sides of the protective strip is removed by means of an ion beam. A plate of the substrate material remains standing between the two troughs formed in this manner, and can then be separated at its periphery from the residual substrate and can be lifted out of the substrate by means of a micromanipulator, wherein the structures of interest are located in the lifted-out plate. A similar process for providing a material plate having a thickness of 5-100 nm is known from the published patent application DE 103 44 643 A1.
However, these generally rectangular material plates are either too thick, or too fragile for high resolution analysis. In patent document U.S. Pat. No. 7,002,152, a preparation method for a partly post-thinned material sample for high resolution electron microscopic studies is described.
This known process is found unsatisfactory in respect of the quality of the material samples (lamellae) so obtained, in particular for high resolution electron microscopy.
The invention assumes that precisely manufactured lamella faces are desirable for such applications.
The known process generates, on the one hand, surfaces which are not sufficiently precisely planar; and on the other hand, the surfaces so generated tend to deform after their manufacture. The present inventors have found that one reason for this is that in the known process, the rim of the sample is weakened. Therefor, any tensions present may distort or bend thin material samples.